DESCRIPTION (provided by investigator): Prescription opioid abuse is becoming an increasingly widespread and serious public health concern. The 2001 National Household Survey on Drug Abuse report revealed that the number of first-time users of prescription opioid medications for non-medical reasons reached 2.0 million in the year 2000, a number that has quintupled since 1984, and the 2002 Drug Abuse Warning Network (DAWN) report showed that the number of emergency department mentions of several prescription opioid medications more than doubled between 1994 and 2001. Despite these trends, little experimental research has been directed towards understanding who may be abusing these medications, and under what conditions. The current application will examine the reinforcing, subjective, performance, and physiological effects of two commonly prescribed opioid medications (oxycodone, codeine) in two separate studies. Because it is not clear who is abusing prescription opioids, the medication effects will be compared in drug abusers and non-drug abusers. And because it is not clear under what conditions these medications are used, the effects of oxycodone and codeine will be examined in the presence and absence of experimentally-induced pain. For each study, one between- [drug use history (drug abusers, non-drug abusers)] and two within-subjects variables [pain condition (pain, no pain); medication dose (placebo, low, high dose)] will be examined. Because previous studies have shown sex differences in response to opioid medications, we will attempt to enroll equivalent numbers of men and women in each study so that we can conduct exploratory analyses of sex differences in response to oxycodone and codeine. The results of these studies will yield important information about who may be abusing prescription opioid medications, and will provide a better understanding of several important variables that may influence the propensity to abuse these medications.